1. Field of the Invention
The invention relates generally to a light-curing system and method. More specifically, the system provides controlled heating of at least two different polymerizable materials within a chamber at two different temperatures. A single source provides the necessary curing light and heat to achieve polymerization of both materials. The first polymerizable material is heated to temperatures within a first temperature range, and the second polymerizable material is heated to temperatures within a second temperature range. The system is particularly suitable for making dental devices such as full dentures, removable partial dentures, relines of full and partial dentures, nightguards, occlusal splints, and the like.
2. Brief Description of the Related Art
Various light-curing systems are known in the dental arts for making dental products. For example, Masuhara et al., U.S. Pat. No. 5,135,686 (“the '686 Patent”) discloses a method for curing light-polymerizable objects by placing the objects on a conveyor belt, which transports the objects through a curing apparatus. The object is conveyed to a first station, where it irradiated with visible light from a first source having relatively low radiation intensity. Moving forward, the object enters a second station, where it is irradiated with visible light from a second light source having relatively high radiation intensity. The objective of the method in the '686 Patent is to control the rate of polymerization so that the object can be fully and uniformly cured. The flux density of the irradiating light needs to be controlled in order that the object does not cure too quickly according to the '686 Patent. In one embodiment, a mixture of light-curing resins was placed in a mold and a tooth specimen was embedded in the resin—the resulting object was placed on a conveyor belt. A first light source irradiated the object with visible light having low intensity. Then, a second light source irradiated the object with high intensity, and the object was polymerized. No cracks were observed in the polymerized object upon removing it from the mold. Thus, in the '686 Patent, multiple light sources having different intensities are used to irradiate the article. The intensity of the irradiated light varies depending upon the position of the article.
Feurstein et al., U.S. Pat. No. 5,922,605 (“the '605 Patent”) discloses a polymerization apparatus for light-curing objects including dental workpieces. The '605 Patent recognizes that the time for light-curing an object can be shortened when the object is also heated. Thus, the '605 Patent describes a process, whereby an object is placed in an apparatus, and a light source is switched on. The light source begins to polymerize the object. After the object has been irradiated with the light for a period of time, for example, 10 minutes, a separate and independent heat source is switched on. Heating takes place for another 10 minutes or other suitable time period. Then, the heating and light sources are switched off, and the object is cooled to end the polymerization cycle. Thus, in the '605 Patent, the heat source is used to heat the article sufficiently so that the time for curing the article is reduced.
Although the foregoing light-curing systems might be somewhat effective, it would be especially desirable to have a system, whereby an integrated lighting and heating source could be used to polymerize and cure the article. In such a system, one lighting source for irradiating the article with light and a second heating source for treating the article with heat would not be needed. Rather, the same single source would provide sufficient light and heat to polymerize the article. A system that used a single source to provide curing light and heat would be advantageous for several reasons. In such a system, the heat generated from the light source could be used to internally melt articles having a partial crystalline structure. At the same time, the light generated by the lighting source would initiate polymerization of the article. The heat would be controlled so that the article did not substantially lose its mechanical integrity or original shape, while the article was polymerized. The light would be controlled so that the article could be uniformly and fully polymerized. A system that produces a polymerized and cured article according to the following steps would be particularly desirable. A first polymerizable material would be light-cured using a lighting and heating source having a temperature within a first temperature range. Then, a second polymerizable material would be positioned on or adjacent to the first polymerized material, and the second material would be light-cured using a lighting and heating source having a temperature within a second temperature range. In such a system, the light and heat should be controlled so that the materials do not substantially change their shapes while ensuring that the materials are polymerized fully. The material must be hardened sufficiently so that it has sufficient mechanical integrity and strength. Such a system could be used advantageously to produce full and partial dentures and other dental devices. The present invention provides such a system.